Perspective:

This study adds to prior work done by this group showing that stress CMR, combined with observation unit care, leads to lower costs compared to hospital admission among intermediate-risk patients with suspected ACS (Miller CD, et al., JACC Cardiovasc Imaging 2011;4:862-70), and supports a growing body of evidence that stress CMR is a safe, effective, and cost-efficient means of risk stratification of patients with suspected ACS. The primary limitations of this study are several. First, this study was conducted at a single center with very high-quality stress CMR imaging. Stress CMR remains unavailable at the vast majority of hospitals, and may be of variable quality and safety at others. Second, among subjects assigned to usual care, the majority underwent stress echocardiography. It is unclear whether results would be different if a more sensitive test were used such as if nuclear imaging had been used instead. Third, no core labs were used. It is unclear whether core lab imaging for stress echocardiography would have improved the outcomes among the usual care group. Finally, observation unit staff were aware that patients were participating in this study, while inpatient staff were blinded to patient participation. This may have led to more cautious behavior among providers caring for observation unit patients, magnifying a difference which may have been smaller or nonexistent outside of the trial setting.